Normal values for the abdominal aorta on ultrasound
This entry summarises sonographic normal values, measurement technique, reporting essentials and referral thresholds relevant to emergency practice in the UK. Clear measurement convention and documentation are critical because surveillance and referral decisions use specific ultrasound measurements (NICE NG156).
Definitions and thresholds
- Normal abdominal aorta: maximum diameter < 3.0 cm on ultrasound.
- Abdominal aortic aneurysm (AAA): maximum diameter ≥ 3.0 cm (NICE NG156).
- Common iliac artery: typically normal < 1.5 cm;
> 1.5 cm is considered aneurysmal in UK PoCUS competency guidance (RCEM).
Note: NICE uses the inner‑to‑inner anterior-posterior (AP) diameter for surveillance and repair thresholds. Some ED/POCUS training materials describe outer‑to‑outer measurements for routine scanning-make local policy explicit and report the convention used.
Measurement technique - key principles
- Measure the maximum AP diameter on transverse (short‑axis) views.
- Obtain multiple transverse images at suprarenal, pararenal and infrarenal levels to identify the true maximum diameter.
- Use longitudinal (long‑axis) views to show extent and relationship to the renal arteries.
- Place calipers perpendicular to the aortic axis and avoid oblique planes that misrepresent diameter.
- Measurement convention:
- For referral and surveillance thresholds use the inner‑to‑inner AP diameter (NICE NG156).